A wooden deck should last about 25 years.  It depends on a couple things.  If the deck was maintained well, it will last longer.  If it gets constant sun exposure, the wood will dry out and it will not last as long.  If the deck is in shade much of the time, it can stay wet for several days after a rain storm.  When wood stays wet, it can rot and mildew and mold can grow.

If you are concerned about your deck, please contact me.